Sulfur-containing polymers and their preparation



Patented Feb. 25, 1947 UNITED STATES PATENT orr cs SULFUR-CONTAINING POLYMERS AND THEIR PREPARATION William J. Burke, Marshallton, Del., asslgnor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing.

- radical and R" is a member of the group consisting of hydrogen atoms and monovalent organic radicals. Another object is to provide new organic solvent-soluble polymeric products having the general formula RSCI-IzX, wherein R. is the residue of an organic solvent-soluble, linear polymer, X is a radical of the group consisting of OR.', SR' and N-R'COR", in which R -is a lower alkyl group and R" is a member of the group consisting of hydrogen atoms and lower alkyl groups. A still further object is to provide new alkoxymethylmercapto derivatives from natural rubber. Still another object is to provide,

a methodfor obtaining said polymeric products.

Additional objects will become apparent from an examination of the following description and claims.

These and other objects and advantages are Application October 154, 1944, Serial No. 558,727

19 Claims. (Cl. 260-7 8) 2 claims, is meant a compound selected from the group consisting of monohydric alcohols, monothiols and monoamides oi monocarboxylic acids, said compound giving a positive reaction for active hydrogen by the Zerewitinoff Test (Ber. 40,

'2023 (1907); ibid 41, 2236 (1908)).

By the term polymeric thioacylate." 'as employed herein and in the appended claims, is meant the product obtained by reacting an organic solvent-soluble, polymeric polyunsaturated organic substance with a monocarbothiolic acid as described in the copending'applications of W. J. Burke, Serial No. 503,417, filed September 22; 1943 and of Lawrence M. Richards SerialNo. 515,807, flledDecember 2'7, 1943.

By "monocarbothiolic acid is meant an acid of the general formula 'RCOSH, wherein R is a monovalent radical of the groupconsisting oi alkyl and aryl radicals.

The following examples, in which proportions are in parts by weight unless otherwise specified,

' are given for illustrative purposes and are not accomplished according to the hereindescribed invention which broadly comprises reacting a linear, organic solvent-soluble, polymeric thio-' acylate with formaldehyde and a monomeric, active hydrogen-containing organic compound in the presence of an acidic compound as catalyst. One preferred embodiment of this invention comprises reacting a benzene solution of a rubber thioacetate with formaldehyde 'and methanol in the presence of a strong acid as catalyst.

Another preferred embodiment comprises reacting a benzene solution of rubber thioacetate with formaldehyde and a N-alkylamide' in the presence of a. strong acid as a catalyst.

. By the term acidic compound," as employed herein and in the appended claims, is meant a B y-the term strong acid," as used herein and in the appended claims, is meant a water-soluble intended to place any restrictions on the herein described invention. 4

Example I Rubber thioacetate is prepared by'reacting 68 parts of rubber with 114 parts of ethanethiolic acid' (1.5 mole/isoprene unit) in 160 parts of benzene at room temperature for 6 days in the acid having a dissociation constant greater than 1x 10-,

By the term "polymer" as employed herein and in the appended claims, is meant a macromolecular organic compound containing a plurality of recurring units which are Joined together in a chain-like manner.

By the term "active hydrogen-containing compound." as used herein and in the appended .bined ethanethiolic acid.

presence of air. The product is precipitated by drowning in methanol and the precipitate is washed with methanol until it is free of uncom- The resulting soft, light-colored product contains 17.85% sulfur, which corresponds to addition of ethanethiolic acid to 66% of the double bonds originally present in the rubber. a

To 8 parts of the-rubber thioacetate, prepared asdescribed above, dissolvedin 16 parts of benzene, is added a solution prepared by dissolving 9 parts 01' paraiormaldehyde in 16 parts of methanol containing 0.005 part 01 sodium hydroxide and diluting with 16 parts of benzene. Dry hydrogen chloride is bubbled through the solution slowly for a few minutes and an additional 24 parts of benzene is added. The reaction mix-' ture is heated under reflux for 2 hours, cooled to room temperature, allowed "to ,stand for 18 hours, filtered to remove a small amount of insoluble material, and then drowned in a methanol-solid carbon dioxide mixture. The soft. light-colored solid thus obtained is washed thoroughly with alcohol and dried in a vacuum desiccator. The product contains 11.32% methoxyl (-cn-cn-en-cm'-) nHCHO (CHaO) and 18.11% sulfur, which corresponds to i j the presence of 0.65 CHaO/S, or stated differently, replacement of 65% of the acetylmercapto groups.

with methoxymethylmercapto groups. 'I'he reactions which occur during the conversion of the thioacyl group to the methoxymethyl group may be represented by the followingequationsz cmon CHIQH B CHOCHI' The product prepared as described above is soluble in dioxane and in aromatic hydrocarbon.

and chlorinated hydrocarbon solvents. Films cast from benzene solution are-clear and pliable.

However, since the product still contains thioacyl groups, it may be rendered insoluble in organic solvents by alkaline hydrolysis followed by oxidation, e. 3. exposure to air, of the hydrolysis product, as represented by the equations shown below.

SCHQOCH;

SCHaOCHs n H Example r:-

the addition .of ethanethiolic acid to 79% of the doublebonds originally present in the rubber, dissolved in 120 parts of benzene under nitrogen is added 24 parts of a methanol solution con-.

t inins 1.5 partsof sodium methylate. After minutesat room temperature, there. is added to the reaction. mixture 9. solution obtained by warming a mixture of 100 parts of isobutylforrnamide (1 mole), 27 parts of paraformaldehyde I 1 (-cH-cn-en-cm) j To parts of the thioacetate of rubber, prej pared essentially as described in Example I, and containing 19.72% sulfur, which corresponds to .as hereinbefore defined.

action mixture is kept at room temperature for 1 hour and then added to a methanol-solid carbon dioxide mixture inorder to precipitate the product. The resulting soft solid is washed several times with fresh methanol, dissolved in 160 parts of acetone, precipitated in a methanol-solid I carbon dioxide mixture and washed thoroughly withmethanol. The product obtained contains 21.9% sulfur and 0.25% nitrogen, which corresponds to the replacement of about 3% of the thioacetate .groups with N-isobutylformamidomethylmercapto substituents. As illustrated by the examples, the compositions of the present invention are had by reacting an organic solvent-soluble polymeric thioacylate with formaldehyde and an active hydrogen-containing compound in a homogeneous system under acid conditions.

Any organic solventsoluble polymeric thioacylate may be used in the practice of this invention. Furthermore, thecorresponding thiols can be used. Of course. it'is to be understood that by corresponding thioi" is meant the thiol had by replacing the thioacyl groups of a polymeric thioacylate with thiol groups. For practical reasons it is'pr'eferred to employ the polymeric thioacylate rather than the corresponding thiol in the practice of this invention since the thioacylates are stable in the'presence of air and in their use no special procedures are required to obtain the desired products of formula RSCHzX,

Polymeric thioacylates useful in of this invention are conveniently made by the methods describedin the copending application of. WilliamJ, Burke, Serial No. 503,417, -flled September '22, 1943, and that of Lawrence M. Rich- 7 ards, Serial No. 515,807, filed'December 27, 1943.

These include the thiols and thioacylates of the from components at least one of which contains at least one olefin double bond; unsaturated alcohol modifled urea-formaldehyde, melamineformaldehyde, and phenol-formaldehyde poly-" mers; unsaturated derivatives of such film-formin; p lymers as starch, polyvinyl alcohol, casein,

etc-., partially polymerized drying oils, e. g.. heat bodied linseed oil and heat-bodied China-wood oil, etc.: the linear diene polymers obtained by polymerizing di'ene hydrocarbons in admixture with one another or in admixture with other polymerizabie organic compounds. Examples of such dienes are butadiene-1,3, isoprene, dimethyl- 2,3-butadiene-1,3 and the like. Examples of unsaturated organic compounds which can be polymerizedwith the above dienes are styrene, pinene,

(0.9 moleiand 0.3 partof 'a.10% solution of. 1

potassium hydroxide in methanol. After the paraformaldehyde has dissolved there isadded 24 parts of a 5% solution of paratoluene-sulfonic acid in acetic acid. The'resultant 1'6" isobutylene, camphene, monovinylacetylene, eta, vinylethinyl alkyl carbinols, vinyl acetate, vinyl chloride-unsaturated aldehydes and ketones such as acrolein, methyl vinyl ketone, etc., acrylic and methacryiic acids and their esters, amides,

imides, and nitriles,'e. g., butyl acrylate, methyl acryionitrile, methacrylonitrile -etc., alpha-chloroacrylic acid and its esters, e. g.,

methacrylate,

methyl alpha-chloroacrylate, octyl alpha-chloroacrylate, eta, furyl acrylic acid andits esters,

e. g., methyl furyi acryiate, etc., esters of 1,4- butenedioic acids, e. g., dimethyl fumarate, di-

the practice I 1.41am

methyl malea'te, etc. In place of the synthetic polymers there can be used naturally occurring unsaturated polymers. e. g., natural rubber, gutta I percha, etc.

Polymeric thioacylates prepared by reaction of a carbothiolic acid with a polymeric N-oxymethylcarbonamide, as described in the copending application of 'W. J. Burke, Serial No. 624,823, filed March 1, 1944, andthe corresponding polythiols can also be used in this invention. pecific types of polymeric thioacylates and particularly thio-' a In place of the paraformaldehyde disclosed in the examples, there maybe employed gaseous formaldehyde itself, or other formaldehyde-proacetates include those prepared in this manner from the N-alkoxymethyl, or N-hydroxymethyl derivatives of polyamides, such as heiianietl'lylene adipamide and decamethylene sebacamide, polyesteramides such as hexamethylene sebacate adipamide, urea-formaldehyde resins including alcohol modified products, etc.

Suitable polymeric thioacylates also includ those prepared by reacting carbothiolic acids, particularly ethanethiolic acid, with organic solvent-soluble, high molecular weight polymers having ethylenically unsaturated side chains attached to the main polymer chain through oxygen- The preparation of these'products and the corresponding polythiols described in the copending application of w. J. Burke, Serial No.

525,093, filed March 4, 1944. Specific suitable polymeric thioacetatesinclude those prepared by the above process from crotyl cellulose, crotyl ducing compounds, e. g. trioxane.

Mcthylol commands such as 2(hydibxymethylmercapto) -thiazoline, and N(hydromethyl) benzamide can be used in place of formaldehyde and the active-hydrogen containing compound.

In the practice of this invention. generally, it is desirable to use at least one mole each of formaldehyde and active hydrogen compound per gram atom of sulfur present as a constituent of a thiol or thioacyiate group. If only a small amount of modification is desired for some specific purpose, smaller quantities of the monomeric reactants can be used. A 1 to 10 mole or greater excess of the monomeric reagents is often used in I order to reduce reaction time and to insure complete-reaction when this is desired. It is generalticularly desirable where soluble products are retaining compounds, it is to be understood that any active hydrogen-containing organic compound as hereinbefore defined is operative th'erein. Included among examples of active hydrogencontaining organic compounds contemplated for use in this process are monomeric compounds which contain hydrogen directly attached to an oxygen, nitrogen or sulfur atom and which are a solvent.

members of the group of alcohols, monothiols and monamides, e. g.,'alcohols, such as methanol,.

isopropyl alcohol, tertiary butyl alcohol, octanol, ethylene chlorohydrin, hydrochloride, Nsethyl-N-hydroxyethyl formamide, lactic acid, methyl hydroxyacetate, and the like; thiols, such as ethanethiol, butanethiol,

paranitrobenzyl mercaptan, cyclohexyl mercaptan, 2-mercapt'othiazoline, mercaptoacetic acid.

dimethylaminoethanol I ethyl mercapto acetate, etc.; monamides, such as a ethane, dioxane, and diethyl ether.

'those derived from 'monocarboxylic acids, and

drogens in the form of hydroxyl or mercapto groups-can also be used and examples are Z-mercaptoethanol, ethylene glycol, etc. Their use makes possible the formation of crosslinked prod- 1y preferred that the mole ratio of activehydrogen' component to formaldehyde be at least 1 to 1. This is particularly trud when soluble products free of crosslinks are desired.

It is to be understood that the reaction of the present invention must be eflected in the presence of an acidic compound as catalyst.

While appreciable eifects are had with any acidic cbmpoundsubstantially improved yields ordinarily result when a strong acid is used as catalyst. Included among examples of strong acids are: hydrochloric acid, paratoluenesulfonlc acid, phosphoric acid, sulfuric acid and the like.

The process is generally operated at temperatures which range from 25 to 100 C. Temperatures up to. decomposition temperature of the reactants or products can be used, if desired. The use of temperatures below 100 C. is parstances the active hydrogen-containing com-- pound can function both as a reactant and as The choice of inert solvent depends primarily on the particular polymer used. Forexample, with rubber thioacetate containing 19 to 22% sulfur, dloxane is a suitable solvent, but with rubber thioacetate having 3-10% sulfur, benzene is much more suitable. With a more polar type of polymer such as N-(acetylthiomethyl)hexamethylene adipamide, acetic acid can be used with advantage, particularly with thiols and amides. With products such as N-acethylthiomethylhexamethylene' sebacamide an excess of a lower aliphatic alcohol can be used-both as a reactant and as a solvent. Other suitable solvent include benzene, toluene, xylene and other aromatic hydrocarbons, trichloroethylene, methylene chloride and the chlorinated aliphatic hydrocarbons, and ethers, such as 1,2-dlm'eth'oxy- It is preferable to carry out the reaction in a homogeneous system since reaction of the solid polyacylates or polythiols with'formaldehyde, active-hydrogen-compound and catalysts results in superficially crosslinked products'whose utility ucts under certain conditions and this, of course,

operates to limit their utility.

is limited. e

As hereinbefore stated, the novel products of this invention are polymeric products having the generalformul'a RSCHzX, wherein R is the residue of a linear. organic solvent-soluble polymer and X is a monovaicnt organic radical of the formulae OR -SR. and

- i 7 group consisting of radicals having the general RI I!I-COR" formaldehyde and a monomeric active hydrogencontainingorganic compound in the presence of an acidic compound as catalyst. Thus, reaction, of a: rubber thioacetate with formaldehyde and the following active hydrogen-containing organiccompounds in the presence of an acidic compound as catalyst provides products containing the characteristic units shown in the table below.

Active 7 hydrogen-containing Characteristic unit in product compound CH: CIHIOH (i:

--CH:CH HC Hz- Butenol A CHQOCaHa CH: ClCHlCHaOH I:

'CH r-CH H+CH:- Ethylene chlorohydrin CHQQOHBCHQCI an N CH -CH1OH:1lH-CHa- Cr-SH N'CH1 (His-S SCHaSC Z-mercaptothlazollne v CH: C'sHaCONHs. r J:

CH:-CH-- HCHr- Benzsmide- I CHINHCOCuHI CuHaBH -CH:CH- H-.--CH Dodecanethioi v CKiCSllEii Similarly by using a butadiene-styrene interpolymer thioacetate in place of the aforementioned rubber thioacetate, there are obtained products which contain the characteristic structural units shown below.

The products of this invention are useful in the preparation of pellicles, fibers, coating compositions and the like.

As many apparently widely different embodiments of this invention may be made without do parting from the spirit and scope thereof, it is to be understood that I do notlimit myself to the specific embodiments thereof except as defined in the appended claims. Having described the present lowing is claimedas new andjuseful: v a

1. A polymeric product having the general formula RSCHzX, wherein R isthe residue of a rubber-like polymer of a diolefin and X is a monovalent organic radical of the group consistingof radicals, having the general formulae OR', -SR' and l l'-COR" wherein R" is a lower alkyl group and R" is a member of the group consisting of, hydrogen atoms and monovalent lower alkyl groups.

2. A polymeric product having the general formula RSCHzOR', wherein R is the residue of a rubber-like polydiolefine and R is a monovalent lower alkyl group; i

3. A polymeric product having the general formula. RSCHzOCHawherein R. is the residue of a rubber-like polydiolefine.

4. A polymeric product havingthe general formula asomi i-oo n" v wherein R is the residue of a rubber-like polydi- I oleflne, R is a monovalent lower alkyl group and R" is a member of the group consisting of hydrogen atoms and monovalent lower alkyl groups.

CHKCHa):

RSCHs-N-COH wherein R isthe residue of a rubber-like polydi- 6. The process for obtaining a polymeric product having the general formula RSCHzX, wherein R is the residue of a rubber-like polymer of a diolefin and X is a monovalent organic radical of invention, the folhydrogen-containing compound are employed per mole of polymeric thioacylate and .the mole ratio of active hydrogen-containing organic compound to formaldehyde is at least 1/ 1.

8. The process for obtaining a polymeric prodwherein R is the residue of a. rubber-like polydiolefine, which comprises reacting a benzene solution of a, thioacetate of a rubber-like polydioleflne with formaldehyde and methanol in the presence of a strong acid as catalyst.

10. The process for obtaining a polymeric product having the general formula ?I RSCHz-NCOR" wherein is the residue of a. rubber-like polydiolfine, R is a monovalent lower alkyl group and not having the general formula RSCHzORTE' not having the general formula RSCH2OCHa,'

R" is a member of the group consisting of hy- I drogen atoms and monovalent lower alkyl groups, which comprises reacting a thioacylate of a rubher-like polydiolefine with formaldehyde and an N-loweralkylamide in the presence of a strong acid as catalyst.

11. The process for obtaining a polymeric product having the general formula CH(CH:):

nsom-rr-oon wherein R is the residue of a rubber-like polydioleflne, which comprises reacting a benzene solution of a thioacetate of a rubber-like polydioleflne with formaldehyde and an N-isobutylforamide in the presence of a strong acid as catalyst.

12. A polymericproduct having the general formula RSCHiOR', wherein R is the residue of rubber and R. is a, monovalent lower alkyl group. 13. A polymeric product having the general formula RSCHrOCHz, wherein R is the residue of rubber.

14. A polymeric product having the general formula nsomr wcon" wherein R is the residue of rubber, R is a monovalent lower alkyl group, and R" is a member of.

the group consisting of hydrogen atoms and monovalent lower alkyl groups.

15. A polymeric product having the general formula omen-)3 RsoHr-N-ooH wherein R is the. residue of rubber.

not having the general formula RSCHzOR', wherein R is the residue of. rubber and R is a monovalent lower alkyl group, which comprises reacting a thioacylate of rubberv with formaldehyde and a lower aliphatic monohydric alcohol in the presence of a strong acid as catalyst.

17. The process for obtaining a polymeric product having the general formula RSCHzOCHa. wherein R is the residue of rubber,- which comprises reacting a benzene solution of a thioacetate of rubber with formaldehyde and methanol in the presence of a strong acid as catalyst.

18. The process for obtaining a polymeric product having the general formula RSCHiIh-COR" wherein R is the residue of rubber, R is a monovalent lower alkyl group, and R" is a member of the group consisting of hydrogen atoms and.

monovalent lower alkyl groups, which comprises reacting a thioacylate of rubber with formaldehyde and an N- lower alkylamide in the presence of a strong acid as catalyst.

' 19. The process for obtaining a polymeric prod-v uct having the general formula CH(CH1):

RSCH:NC 0H wherein R is the residue, of rubber, which comnnrnnnucns orrr-zn The following references are of record in the file of this patent:

FOREIGN PATENTS Number Country Date 514,535 British, Deut. Hydro.

Akt. Ges. Nov. 10, 1939 .7 9 German I. G. F. Apr. 30, 1932 

